THE ULTRASTRUCTURE OF HUMAN AND MURINE ASTROCYTES AND OF HUMAN FIBROBLASTS IN CULTURE

Abstract

A study was undertaken to seek fine structural differences between normal and maglinant astrocytes and normal fibroblasts in cell culture. A series of human adult normal astrocytes and malignant astrocytes (including RSV‐transformed cells) whose cultural characteristics had previously been reported formed the basis of the study. Also included were matched normal human fetal fibroblasts and astrocytes (from the same fetus) and methylcholanthrene‐induced murine malignant astrocytes. Pellets of cells scraped from their culture vessel and sectioned as well as in situ preparations were examined. The fibroblasts were the only cells whose external microfibrils were collagenase‐sensitive and considered to be tropocollagen. Both the benign and the malignant astrocytes had intracytoplasmic microfibril bands (gliofibrils) and some had external collagenase‐resistant microfibrils. Malignant astrocytes had a much more developed membrane system (used in its widest sense) than normal astrocytes, had many free ribosomes and some had morphologically abnormal mitochondria. Virus was seen only in the murine malignant astrocytes, was abundant and of the murine leukemia virus group. Areas interpreted as representing fusion in progress were seen at the surface of some RSV‐transfomed giant tumor astrocytes. The fine structure of one cell type from an IgG‐producing culture from human glioblastoma corresponded with that reported for immunocytes.